The present invention relates to finger oximeters and more particularly to a finger oximeter having a suspension system that enables the finger gripping portions of the oximeter to firmly and evenly grasp a patient""s finger.
There are a number of known finger oximeters. Generally, these finger oximeters are pulse oximetry units that utilize a sensor, and a coacting photodetector that detects the light emitted by the sensor, for determining the blood oxygen saturation of the arterial blood passing through the finger of a subject. To illuminate the finger of the subject, and to detect the light passing through the subject""s finger, a prior art finger oximeter usually would have a finger gripping mechanism that has two finger gripping portions. The prior art teaches that these finger gripping portions hingedly coact with each other, usually by pivots. The following U.S. patents specifically disclose finger gripping portions that open to accept a finger via some hinge mechanism that enables the finger gripping portions of the finger oximeter to pivot about one end point of the finger oximeter: U.S. Pat. Nos. 4,685,464; 5,490,523; 5,792,052; 5,313,940; 5,676,139; 5,810,724; 5,957,840; and 6,041,247.
There are other methods of enclosing two finger gripping portions about a finger. One such method is the taping of a finger to a photodetector by means of a tape that has a light emitter, as disclosed in U.S. Pat. No. 5,209,230. Another method clamps two finger gripping portions together by means of coacting teeth at the respective sidewalls of the finger gripping portions. This is disclosed in U.S. Pat. No. 5,339,810. The use of a single piece U-shaped flexible holder that expands with the insertion of a finger is disclosed in U.S. Pat. No. 5,311,865.
For those finger oximeters that use two piece finger gripping portions which are tightened by coacting grasping teeth at their respective sidewalls, there is the disadvantage that it is difficult to remove the finger from the finger gripping portions since the finger gripping portions are locked at a given dimension. And for those finger oximeters that utilize a hinged pivoting mechanism, the force that the finger gripping portions applies to a finger tends to be uneven along the finger, and gets weaker the further the finger is away from the hinged location.
The present invention finger oximeter has a floating suspension system that results from one of the finger gripping portions being movable vertically relative to the other finger gripping portion, which is fixed. A biasing force is applied against the movable finger gripping portion so that the movable finger gripping portion is constantly biased towards the fixed finger gripping portion. The two coacting finger gripping portions are configured such that their opposing surfaces are contoured to form an opening for accepting a finger inserted therebetween. The biasing force applied against the movable finger gripping portion is such that the movable finger portion is yieldable when a finger is inserted between the fixed and movable finger portions, and yet at the same time has a sufficient large biasing force to push the movable finger portion towards the fixed finger gripping portion with an even distribution of force along the length of the finger, to thereby cause the two finger gripping portions to firmly grasp the finger placed therebetween.
The force applied against the movable finger gripping portion to bias it towards the fixed finger gripping portion is supplied by a plurality of coiled springs interposed between the movable finger gripping portion and a casing along which sidewalls the movable finger gripping portion guidingly moves. The springs may be secured to ledges extending from the lower portion of the respective sidewalls of the casing so that the biasing force is applied against the movable finger gripping portion in such a way that the movable finger gripping portion is movable vertically with respect to the fixed finger gripping portion.
The fixed finger gripping portion may be mounted to the upper part of the casing, and is configured such that its upper surface is adaptable to receive a printed circuit board that has mounted thereto or etched thereon a number of electronic components or circuits that effect the operation of the finger oximeter. A display, LED or otherwise, is also mounted to the PC circuit board for displaying values that represent the physical parameters of the patient measured via the patient""s finger.
The finger gripping portions are further configured to have respective apertures through which light from a light emitter may be directed from one of the finger gripping portions to a corresponding aperture of the other finger gripping portion, which is equipped with a receptive photodetector.
To power the finger oximeter of the instant invention, a battery pack or module is mounted to the underside of the movable finger gripping portion so as to move in unison with the movable finger gripping portion. To operate, a user needs to manually activate a switch mounted to the casing. To conserve energy, the device is automatically turned off after a predetermined time period, if it no longer is in use.
It is therefore an objective of the present invention to provide a finger oximeter that has a floating suspension system.
The finger oximeter of the instant invention has the further objective of evenly distributing the gripping force applied by its finger gripping portions to the being gripped finger.